Aqueous heat-transferable inkjet ink sets and processes for using the same

Abstract

In a first aspect, an aqueous heat-transferable inkjet ink set includes a heat-transferable white ink and non-white colored inks. The heat-transferable white ink includes 5-15 wt% titanium dioxide pigment, 5 to 25 wt% polyurethane binder, 0.1 to 5 wt% blocked isocyanate crosslinker and 0.1-1.5 wt% surfactant. The polyurethane binder is a blend with a ratio in a range of from 0.8:1 to 21:1 of a polyester polyurethane to a polycarbonate polyurethane. The aqueous heat-transferable ink set is adherable to a textile surface by heat-transfer. In a second aspect, a process for digitally printing an image on a Direct-to-Film (DTF) substrate and heat-transferring a printed image to a textile fabric is provided.

Description

TITLEAQUEOUS HEAT-TRANSFERABLE INKJET INK SETS AND PROCESSES FOR USING THE SAMEFIELD OF DISCLOSURE

[0001] The field of this disclosure is aqueous heat-transferable inkjet ink sets and processes for digital printing an image on a Direct-to-Film (DTF) substrate and heattransferring a printed image to a textile fabric.BACKGROUND OF THE DISCLOSURE

[0002] Inkjet digital printing has become more widely used in the printing of textiles. It offers a number of potential benefits over conventional printing methods such as screen printing. Digital printing eliminates the set-up expense associated with screen preparation and can potentially enable cost-effective short run production. Digital printing furthermore allows visual effects, such as tonal gradients and repeat of printed patterns that cannot be practically achieved with a screen-printing process. Especially beneficial is the ease in changing the patterns of originals during production of digital printing, when it is possible to respond to a change in patterns or other requirements within a short period of time.

[0003] However, it is difficult for the textile fabrics to directly accept aqueous pigment inkjet inks, even more challenging for synthetic fabrics including polyester, polypropylene, polyurethane, nylon, Nomex® fiber, and Kevlar® fiber due to limited ink absorbency and surface hydrophobicity. The lack of adhesion to textile fabric makes the pigmented inkjet-printed fabrics susceptible to color removal by abrasion and washing. It is known in the art, such as the methods disclosed in European Patent No.2 059 634 B1 , to apply a fabric pre-treatment followed by a heat-transferable white ink base layer before printing colored inks, to achieve improved color strength and washfastness. However, polymer present in the pre-treatment solution necessary for washfastness not only leaves stain, but also causes the fabric to loss its elasticity, stretchiness, and soft hand-feel. Even more challenging is to print on a color dyed synthetic fabric, especially polyester colored by disperse dye. Migration of the disperse dye on the fabric to the heat-transferable white ink layer during high temperature curingof the white and color inks often results in discoloring of the heat-transferable white ink layer and poor image quality.

[0004] In recent times, instead of directly printing onto textile fabric, a transfer printing process, Direct-to-Film (DTF) process, has shown rapid growth. During the DTF process, inks are first printed onto a DTF film. After printing is completed, a thermoplastic polyurethane (TPU) based adhesive powder is sprayed on top of the ink and forms a heat sealable adhesive layer after ink and powder are heated and dried. The DTF film is then heat pressed onto a textile fabric with the TPU layer in contact with the shirt. The TPU heat seal layer is melted under the heat to glue the film to the textile fabric. Afterwards the releasable base film is peeled away, leaving the image adhere to the textile fabric. In comparison with direct printing processes, the DTF process works on broad range of textile fabrics, providing brilliant color and excellent washability. However, the thick TPU adhesive layer between the ink and textile fabric leads to rigid hand feel and an armor-like wearing experience for printed garments. In addition, handling and spraying TPU powders present health and safety concerns.

[0005] A need exists for providing images with good color and durability on a range of textile fabrics, while retaining the elasticity of the textile fabric.DETAILED DESCRIPTION

[0006] In a first aspect, an aqueous heat-transferable inkjet ink set includes a heat- transferable white ink and non-white colored inks. The heat-transferable white ink includes 5-15 wt% titanium dioxide pigment, 5 to 25 wt% polyurethane binder, 0.1 to 5 wt% blocked isocyanate crosslinker and 0.1-1 .5 wt% surfactant. The polyurethane binder is a blend with a ratio in a range of from 0.8:1 to 21 :1 of a polyester polyurethane to a polycarbonate polyurethane. The aqueous heat-transferable ink set is adherable to a textile surface by heat-transfer.

[0007] In a second aspect, a process for digitally printing an image on a Direct-to- Film (DTF) substrate and heat-transferring a printed image to a textile fabric includes: a) providing the DTF substrate b) jetting aqueous non-white colored inks on the DTF substrate; c) jetting an aqueous heat-transferable white ink on the aqueous non-white colored inks, wherein the aqueous heat-transferable white ink includes 5-15 wt% titaniumdioxide pigment, 5 to 25 wt% polyurethane binder, 0.1 to 5 wt% blocked isocyanate crosslinker and 0.1-1 .5 wt% surfactant, wherein the polyurethane binder is a blend with a ratio in a range of from 0.8:1 to 21 :1 of a polyester polyurethane to a polycarbonate polyurethane; d) heating the DTF substrate to dry the inks; e) laying the DTF substrate on top of the textile fabric with the aqueous heat- transferable white ink in contact with the textile fabric; f) pressing the DTF substrate and textile fabric together with heat and pressure; and g) peeling the DTF substrate away with the printed image transferred from the DTF substrate to the textile fabric.

[0008] Although methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention, suitable methods and materials are described herein.

[0009] Unless stated otherwise, all percentages, parts, ratios, etc., are by weight.

[0010] When an amount, concentration, or other value or parameter is given as either a range, preferred range or a list of upper preferable values and lower preferable values, this is to be understood as specifically disclosing all ranges formed from any pair of any upper range limit or preferred value and any lower range limit or preferred value, regardless of whether ranges are separately disclosed. Where a range of numerical values is recited herein, unless otherwise stated, the range is intended to include the endpoints thereof, and all integers and fractions within the range. It is not intended that the scope of the invention be limited to the specific values recited when defining a range.

[0011] As used herein, the term “dispersion” means a two-phase system wherein one phase consists of finely divided particles (often in a colloidal size range) distributed throughout a bulk substance, the particles being the dispersed or internal phase and the bulk substance being the continuous or external phase.

[0012] As used herein, the term “dispersant” means a surface-active agent added to a suspending medium to promote uniform and maximum separation of extremely fine solid particles often of colloidal sizes. For pigments, the dispersants are most oftenpolymeric dispersants, and the dispersants and pigments are usually combined using a dispersing equipment.

[0013] As used herein, the term “aqueous vehicle” refers to water or a mixture of water and at least one water-soluble, or partially water-soluble (i.e. , methyl ethyl ketone), organic solvent (co-solvent).

[0014] As used herein, the term “substantially” means being of considerable degree, almost all.

[0015] As used herein, the term “dyne / cm” means dyne per centimetre, a surface tension unit.

[0016] As used herein, the term “cP” means centipoise, a viscosity unit.

[0017] In describing certain polymers, it should be understood that sometimes applicants are referring to the polymers by the monomers used to make them or the amounts of the monomers used to make them. While such a description may not include the specific nomenclature used to describe the final polymer or may not contain product-by-process terminology, any such reference to monomers and amounts should be interpreted to mean that the polymer is made from those monomers or that amount of the monomers, and the corresponding polymers and compositions thereof.

[0018] The materials, methods, and examples herein are illustrative only and, except as specifically stated, are not intended to be limiting.

[0019] As used herein, the terms “comprises,” “comprising,” "includes," "including," "has," "having" or any other variation thereof, are intended to cover a non-exclusive inclusion. For example, a method, process, article, or apparatus that comprises a list of elements is not necessarily limited only those elements but may include other elements not expressly listed or inherent to such method, process, article, or apparatus. Further, unless expressly stated to the contrary, "or" refers to an inclusive or and not to an exclusive or. For example, a condition A or B is satisfied by any one of the following: A is true (or present) and B is false (or not present), A is false (or not present) and B is true (or present), and both A and B are true (or present).

[0020] Also, use of the “a” or “an” are employed to describe elements and components of the invention. This is done merely for convenience and to give a generalsense of the invention. This description should be read to include one or at least one and the singular also includes the plural unless it is obvious that it is meant otherwise.

[0021] It will be understood that although the terms first, second, third, etc. may be used herein to describe various elements, components, regions, layers and / or sections, these elements, components, regions, layers, and / or sections should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer and / or section from another element, component, region, layer and / or section. Thus, a first element, component, region, layer and / or section could be termed a second element, component, region, layer and / or section without departing from the teachings of the present invention. Similarly, the terms "top" and "bottom" are only relative to each other. It will be appreciated that when an element, component, layer or the like is inverted, what is the "bottom" before being inverted would be the "top" after being inverted, and vice versa. When an element is referred to as being "on" or "disposed on" another element, it means positioning on or below the object portion, but does not essentially mean positioning on the upper side of the object portion based on a gravity direction, and it can be directly on the other element or intervening elements may be present therebetween. In contrast, when an element is referred to as being "directly on" or "disposed directly on" another element, there are no intervening elements present.

[0022] Further, it will also be understood that when one element, component, region, layer and / or section is referred to as being "between" two elements, components, regions, layers and / or sections, it can be the only element, component, region, layer and / or section between the two elements, components, regions, layers and / or sections, or one or more intervening elements, components, regions, layers and / or sections may also be present. Colored Ink

[0023] A colored ink according to the embodiments refers to an ink comprising a colorant. A colored ink can include a heat-transferable white ink. When a heat- transferable white ink is to be excluded from the colored ink(s), the term “non-white colored ink(s)” is used.Colorants

[0024] A colorant used for printing a colored image may be a dye or a pigment. Dyes include disperse dyes, reactive dyes, acid dyes and the like. The term “pigment” as used herein means an insoluble colorant that requires to be dispersed with a dispersant and processed under dispersive conditions in the presence of a dispersant. Pigments also includes dispersed dyes. In some embodiments, pigmented inks are preferred.

[0025] Pigments suitable for being used are those generally well-known in the art for aqueous inkjet inks. The selected pigment(s) may be used in dry or wet form. For example, pigments are usually manufactured in aqueous media, and the resulting pigments are obtained as a water-wet presscake. In presscake form, the pigment does not agglomerate to the extent it would in dry form. Thus, pigments in water-wet presscake form do not require as much mixing energy to de-agglomerate in the premix process as pigments in dry form. Representative commercial dry pigments are listed in U.S. Patent No. 5,085,698 A.

[0026] Some examples of pigments with coloristic properties useful in inkjet inks include, but are not limited to: cyan pigments from Pigment Blue 15:3 and Pigment Blue 15:4; magenta pigments from Pigment Red 122 and Pigment Red 202; yellow pigments from Pigment Yellow 14, Pigment Yellow 74, Pigment Yellow 95, Pigment Yellow 110, Pigment Yellow 114, Pigment Yellow 128 and Pigment Yellow 155; red pigments from Pigment Orange 5, Pigment Orange 34, Pigment Orange 43, Pigment Orange 62, Pigment Red 17, Pigment Red 49:2, Pigment Red 112, Pigment Red 149, Pigment Red 177, Pigment Red 178, Pigment Red 188, Pigment Red 254, Pigment Red 184, Pigment Red 264 and Pigment Red PV19; green pigments from Pigment Green 1 , Pigment Green 2, Pigment Green 7 and Pigment Green 36; blue pigments from Pigment Blue 60, Pigment Violet 3, Pigment Violet 19, Pigment Violet 23, Pigment Violet 32, Pigment Violet 36 and Pigment Violet 38; and black pigment carbon black. The pigment names and abbreviations used herein are the “C.l.” designation for pigments established by Society of Dyers and Colourists, Bradford, Yorkshire, UK and published in “The Color Index”, Third Edition, 1971.

[0027] In one embodiment, a pigment for an aqueous pigmented heat-transferable white ink is titanium dioxide. Titanium dioxide (TiC ) pigment may be in the rutile or anatase crystalline form. It is commonly made by either a chloride process or a sulfate process. In the chloride process, TiCta is oxidized to TiCh particles. In the sulfate process, sulfuric acid and ore containing titanium are dissolved, and the resulting solution goes through a series of steps to yield TiO2. Both the sulfate and chloride processes are described in greater detail in “The Pigment Handbook”, Vol. 1 , 2nd Ed., John Wiley & Sons, NY (1988), the relevant disclosure of which is incorporated by reference herein for all purposes as if fully set forth.

[0028] Titanium dioxide particles can have a wide variety of average particle sizes of 1 pm or less, depending on the desired end use application of the ink. For applications demanding high hiding or decorative printing applications, titanium dioxide particles can have an average size of less than 1 pm (1000 nm). In one embodiment, the particles have an average size in a range of from 50 to 950 nm, or from 75 to 750 nm, or from 100 to 500 nm. These titanium dioxide particles are commonly called pigmentary TiO2.

[0029] For applications demanding white color with some degree of transparency, the pigment preference is “nano” titanium dioxide. “Nano” titanium dioxide particles typically have an average size ranging from 10 to 200 nm, or 20 to 150 nm, or from 35 to 75 nm. An ink comprising nano titanium dioxide can provide improved chroma and transparency, while still retaining good resistance to light fade and appropriate hue angle. A commercially available example of an uncoated nano grade of titanium oxide is P-25, available from Evonik (Parsippany, NJ).

[0030] In one embodiment, titanium dioxide pigment may be substantially pure titanium dioxide or may contain other metal oxides, such as silica, alumina and zirconia. Other metal oxides may become incorporated into the pigment particles, for example, by co-oxidizing or co-precipitating titanium compounds with other metal compounds. If co-oxidized or co-precipitated metals are present, they are present as the metal oxide in an amount from 0.1 to 20 wt%, or from 0.5 to 5 wt%, or from 0.5 to 1 .5 wt%, based on the total titanium dioxide pigment weight.

[0031] In one embodiment, titanium dioxide pigment may also have one or more metal oxide surface coatings. These coatings may be applied using techniques knownby those skilled in the art. Examples of metal oxide coatings include silica, alumina, alumina-silica, boria and zirconia, among others. Such coatings may optionally be present in an amount of from 0.1 to 10 wt%, or from 0.5 to 3 wt%, based on the total weight of the titanium dioxide pigment. These coatings can provide improved properties including reducing the photoreactivity of the titanium dioxide. Commercial examples of such coated titanium dioxides include R700 (alumina-coated, available from The Chemours Co., Wilmington, DE), RDI-S (alumina-coated, available from Kemira Industrial Chemicals, Helsinki, Finland), R706 (available from Chemours) and W-6042 (a silica alumina treated nano grade titanium dioxide from Tayco Corporation, Osaka Japan).

[0032] In one embodiment, titanium dioxide pigment may also have one or more organic surface coatings, such as, for example, carboxylic acids, silanes, siloxanes and hydrocarbon waxes, and their reaction products with the titanium dioxide surface. The amount of organic surface coating, when present, generally ranges from 0.01 to 6 wt%, or from 0.1 to 3 wt%, or from 0.5 to 1.5 wt%, or 1 wt%, based on the total weight of the pigment.Polymeric Dispersant for Colorant

[0033] A polymeric dispersant for colorant may be a random or a structured polymer. Typically, the polymer dispersant is a copolymer of hydrophobic and hydrophilic monomers. A “random polymer” means polymers where molecules of each monomer are randomly arranged in the polymer backbone. For a reference on suitable random polymeric dispersants, see U.S. Patent No. 4,597,794 A. A "structured polymer” means polymers having a block, branched, graft or star structure. Examples of structured polymers include AB or BAB block copolymers such as the ones disclosed in U.S. Patent No. 5,085,698 A; ABC block copolymers such as the ones disclosed in EP Patent Specification No. 0 556 649 B1 ; and graft polymers such as those disclosed in US Patent No. 5,231 ,131 A. Other polymeric dispersants that can be used are described, for example, in U.S. Patent Nos. 6,117,921 A, 6,262,152 B1 , 6,306,994 B1 and 6,433,117 B1.

[0034] In one embodiment, a “random polymer” may also include a polyurethane. Particularly useful is the polyurethane dispersant disclosed in U.S. Patent ApplicationPublication No. 2012 / 0214939 A1 where the polyurethane dispersant is crosslinked after dispersing a pigment to form a pigment dispersion.Preparation of Colorant Dispersions

[0035] Colorant dispersions used in this invention can be prepared using any conventional milling process known in the art. Most milling processes use a two-step process involving a first mixing step followed by a second grinding step. The first step comprises mixing of all the ingredients, that is, colorants, dispersants, liquid carriers, neutralizing agent and any optional additives to provide a blended “premix”. Typically, all liquid ingredients are added first, followed by the dispersants, and lastly the colorant. Mixing is generally done in a stirred mixing vessel, and a high-speed disperser (HSD) is particularly suitable for the mixing step. A Cowels type blade attached to the HSD and operated at from 500 to 4000 rpm, and more typically from 2000 to 3500 rpm, provides optimal shear to achieve the desired mixing. Adequate mixing is usually achieved after mixing under the conditions described above for a period of from 15 to 120 minutes.

[0036] The second step comprises grinding of the premix to produce a colorant dispersion. Typically, grinding involves a media milling process, although other milling techniques can also be used. In the present invention, a lab-scale Eiger Minimill (Model M250, VSE EXP) manufactured by Eiger Machinery Inc., Chicago, IL is employed.Grinding is accomplished by charging about 820 grams of 0.5 YTZ® zirconia media to the mill. The mill disk is operated at a speed between 2000 and 4000 rpm, and typically between 3000 and 3500 rpm. The dispersion is processed using a re-circulation grinding process with a typical flow rate through the mill at between 200 to 500 grams / minute, and more typically at 300 grams / minute. The milling may be done using a staged procedure in which a fraction of the solvent is held out of the grind and added after milling is completed. This is done to achieve optimal rheology that maximizes grinding efficiency. The amount of solvent held out during milling varies by dispersion and is typically between 200 to 400 grams for a batch size with a total of 800 grams. Typically, the dispersions of the present invention are subjected to a total of 4 hours of milling.

[0037] For black pigment dispersions, an alternate milling process using a microfluidizer can be used. Microfluidization is a non-media milling process in whichmilling is done by pigment impingement through nozzles under high pressures. Typically, pigment dispersions are processed at 15,000 psi with a flow rate of 400 grams / minute for a total of 12 passes through the mill. In one embodiment, a lab-scale high pressure pneumatic microfluidizer (Model M-110Y, available from Microfluidics International Corp., Newton, MA) with a diamond Z Chamber may be employed.

[0038] Fillers, plasticizers, silica sols, other polymer dispersions and the known leveling agents, wetting agents, antifoaming agents, stabilizers, and other additives known for the desired end use, may also be incorporated into the dispersions.

[0039] The range of useful particle size of the colorant dispersions is typically in a range of from 0.005 to 15 pm. In one embodiment, the particle size may range from 0.005 to 5 pm, or from 0.005 to 1 pm. The average particle size as measured by dynamic light scattering is less than 500 nm, typically less than 300 nm.White Pigment Dispersion

[0040] One or more dispersants described for colored pigment may be employed to stabilize the titanium dioxide white pigment. It is generally desirable to make the stabilized TiO2 pigment in concentrated slurry form. TiO2 slurry may be prepared in a stirred mixing vessel, and a high-speed disperser (HSD) is particularly suitable for the mixing step. A Cowels type blade attached to the HSD and operated at from 500 to 4000 rpm, and more typically from 2000 to 3500 rpm, provides optimal shear to achieve the desired mixing. Adequate mixing is usually achieved after mixing under the conditions described above for a period of from 15 to 600 minutes. In one embodiment, the amount of titanium dioxide present in the slurry composition is in a range of from 35 to 80 wt%, or from 50 to 75 wt%, based on the total weight of the slurry. In one embodiment, the titanium dioxide has a 50% average particle size (hereinafter referred to as "Dso") that is in a range of from 50 to 500 nm, or from 150 to 350 nm. The titanium dioxide having a D50 within these ranges enables printed film to exhibit satisfactory opacity of the image, which enables formation of an image with high quality.

[0041] In one embodiment, for colored pigments, the ink may contain up to 30 wt% pigment based on the total ink weight. In one embodiment, the colored pigment ink may contain pigment in a range of from 0.1 to 25 wt%, or from 0.25 to 10 wt%, based on the total ink weight. If TiCh white pigment is selected, the ink will tend to contain higherweight percentages of pigment than with comparable inks employing color pigment and may be as high as about 75% in some cases, since TiO2 white pigments generally have higher specific gravities than color pigments.Crosslinking of Polymeric Dispersant

[0042] In one embodiment, a polymeric dispersant dispersing a pigment may be crosslinked after a pigment dispersion is prepared to form a crosslinked pigment dispersion prior to its inclusion in an inkjet ink.

[0043] To enable crosslinking, a polymeric dispersant is substituted with crosslinkable moieties which may be selected from the group consisting of acetoacetoxy, acid, amine, epoxy, hydroxyl, blocked isocyanates and mixtures thereof. Upon introduction of a crosslinking agent to a pigment dispersion, crosslinking of the polymeric dispersant occurs to form a crosslinked pigment dispersion. Typically, a crosslinking agent is selected from a group consisting of acetoacetoxy, acid, amine, anhydride, epoxy, hydroxyl, isocyanates, blocked isocyanates and mixtures thereof. After crosslinking of a pigment dispersion, any excess polymeric dispersant can be removed by purification processes such as ultrafiltration.

[0044] Specific examples of crosslinking moiety / agent pairs are hydroxyl / isocyanate and acid / epoxy.Polymeric Binder for Non-White Colored Inks

[0045] A binder is a polymeric compound or a mixture of polymeric compounds that is added to an ink formulation. The polymeric binder can impart properties to the printed material that, for example, gives greater durability to the printed material. For non-white colored inks, typical polymers used as binders include polyurethane dispersions and polyurethane solutions, acrylics, styrene acrylics, styrene butadienes, styrene butadiene acrylonitriles, neoprenes, ethylene (meth)acrylic acids, ethylene vinyl acetate emulsions, latexes and the like. The binder may be a solution or stabilized as an emulsion by having ionic substituents such as carboxylic acids, sulfur containing acids, amine groups, and other similar ionic groups. Alternatively, the binder may be stabilized by external surfactants. The binder can be used singly or in combination with other binders. The binder is typically present in an ink in an amount of at least 0.2 wt% based on the total weight of the ink. Typically, a binder is different from dye andpigment dispersant described above. The binder is typically added to an ink during the final formulation stage, not during the preparation of a pigment dispersion.

[0046] In one embodiment, a polymeric binder for non-white colored inks can be used singly or in combination with other binders. Typically, the binder is a polyurethane. An optional polyurethane binder is one that is partially, e.g., less than 50%, soluble in THF, as disclosed in U.S. Patent No. 9,255,207 B2, to enhance the durability of the printed image of an inkjet ink. The disclosure of U.S. Patent No. 9,255,207 B2 is incorporated by reference herewith for all purposes as if fully set forth.

[0047] In one embodiment, a polymeric binder for non-white colored inks is present in an ink in an amount of at least 0.2 wt% based on the total weight of the ink. In one embodiment, a polymeric binder for non-white colored inks is present in an ink in an amount of from 1 to 15 wt% based on the total weight of the ink.Polymer binder for Heat-Transferable White Ink

[0048] In one embodiment, a heat-transferable white ink is an inkjet ink which includes a polymeric resin acting as an adhesive binder. The terms “polymeric resin” and “polymeric binder” may be used interchangeably for the heat-transferable white ink. The polymeric resin can be used singly or in combination with other polymers. In one embodiment, a polymeric binder for a heat-transferable white ink is an aqueous polyurethane dispersion. A polyurethane dispersion is typically stabilized as an emulsion particle by having ionic substituents such as carboxylic acids, sulfur containing acids, and other similar ionic groups. Co-stabilizers that are non-ionic in nature, such as those containing polyethylene oxide, may also be present. Alternatively, the polyurethane dispersion may be stabilized by external surfactants. Means of stabilization of the polyurethane particle is not limited to any particular technique as long as the polyurethane polymer is stable in aqueous inks in dispersed particle form. In one embodiment, polyurethane binder is present in a heat-transferable white ink in an amount of at least 5 wt% based on the total weight of the ink. In one embodiment, the polyurethane binder is present in a heat-transferable white ink in an amount in a range of from 5 to 25 wt% percent, or from 7 to 23 wt% percent, or from 8 to 20 wt% based on the total weight of the ink. In one embodiment, to function as an adhesive in a heat- transferable white ink, a glass transition temperature (Tg) of a polyurethane binder is10°C or less, or 5°C or less, or 0°C or less when measured by differential scanning calorimetry (DSC).

[0049] In one embodiment, a polyurethane binder for a heat-transferable white ink is a blend of a polyester polyurethane and a polycarbonate polyurethane. A polyester polyurethane dispersion is a polyurethane polymer having an ester bond and urethane bond in the main chain in addition to the stabilizer groups. A polycarbonate polyurethane dispersion is a polyurethane polymer having a carbonate bond and urethane bond in the main chain in addition to the stabilizer groups. In one embodiment, a polyurethane binder for a heat-transferable white ink is a blend of these two types of polyurethane, with a ratio of polyester polyurethane to polycarbonate polyurethane in a range of from 0.8:1 to 21 :1 , or from 1 :1 to 10:1 , or from 1 :1 to 6.5:1. Although not bound by theory, it is believed polyester polyurethane contributes excellent adhesion to the fabric while polycarbonate type polyurethane brings in improved mechanical strength and toughness which lead to improved rub and washfastness after the ink print is transferred and adhered to the fabric.

[0050] An ester bond in a polyester polyurethane is typically derived from reaction of isocyanate and polyester polyols. Suitable polyester polyols are polyester with two hydroxy groups at two chain ends with a molecular weight of 100 to 4000, or hydroxy number from 28 to 800. Examples of polyester polyols include, but are not limited to, esters derived by reacting acid components with poly(alkylene glycol)s, dihydric alcohols, and trivalent and higher valent alcohols. Examples of the acid components include, but are not limited to, aromatic dicarboxylic acids, alicyclic dicarboxylic acids, and aliphatic dicarboxylic acids. Examples of aromatic dicarboxylic acids include, but are not limited to, isophthalic acid, terephthalic acid, orthophthalic acid, 1 ,4- naphthalenedicarboxylic acid, 2,5-naphthalenedicarboxylic acid, 2,6- naphthalenedicarboxylic acid, biphenyldicarboxylic acid, and tetrahydrophthalic acid. Examples of alicyclic dicarboxylic acids include, but are not limited to, hydrogenated compounds of the aromatic dicarboxylic acids described above. Examples of aliphatic dicarboxylic acids include, but are not limited to, malonic acid, succinic acid, tartaric acid, oxalic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, alkylsuccinic acids, linoleic acid, maleic acid, fumaric acid, mesaconicacid, citraconic acid, and itaconic acid. Reactive derivatives of these acid components, such as acid anhydrides, alkyl esters, and acid halides, can also be used as acid components of polyester polyols. The acid components of polyester polyols may be used alone or in combination. Examples of suitable poly-alcohols are ethylene glycol, 1 ,2-propanediol, 1 ,3-propanediol, 1 ,3-butanediol, 1 ,4-butanediol, 1 ,4-butenediol, 1 ,4- butynediol, 1 ,5-pentanediol, neopentyl glycol, bis(hydroxymethyl)cyclohexanes such as 1 ,4-bis(hydroxymethyl)cyclohexane, 2-methyl-1 ,3-propanediol, methylpentanediols, and also diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, dipropylene glycol, polypropylene glycol, dibutylene glycol and polybutylene glycols. Preference is given to alcohols of the formula HO — (CH2)x-OH, where x is a number from 1 to 20, preferably an even number from 2 to 20. Examples of such alcohols are ethylene glycol, 1 ,4-butanediol, 1 ,6-hexanediol, 1 ,8-octanediol and 1 ,12-dodecanediol. Preference extends to neopentyl glycol. These polyester polyols may be used alone or in combination.

[0051] Examples of useful polyester polyurethane dispersions include, but are not limited to, Takelac™ W-5030, WS-5000 and WS-4022 from Mitsui Chemical (Tokyo, Japan); Impranil® DLN 1623 from Covestro (Leverkusen, Germany); Sancure® 20025F, 835, 2026, 777 and 1301 from Lubrizol (Wickliffe, OH); Superflex® 210, 740, 620, 820 and 500M from DKS Co. (Kyoto, Japan); Hydran® AP-20, 201 , 140SF and HW-171 from DIC Co. (Tokyo, Japan).

[0052] A carbonate bond in a polycarbonate polyurethane is typically derived from reaction of isocyanate and polycarbonate polyols. Suitable polycarbonate polyols are polycarbonate with two hydroxy groups at two chain ends with a molecular weight of 100 to 4000, or hydroxy number from 28 to 800. Polycarbonate polyols include, but are not limited to, polycarbonate diols produced by known methods, for example, polycarbonate diols produced by the reaction between an aliphatic diol component, cited above as alcohol components for the polyester polyol, and phosgene or a carbonate component, such as an alkylene carbonate, a diary carbonate, or a dialkyl carbonate. These polycarbonate diols may be used alone or in combination.

[0053] Examples of useful polycarbonate polyurethane dispersions include, but are not limited to, Takelac™ W-6110 , WS-5100 and WS-4000 from Mitsui Chemical(Tokyo, Japan); Impranil® DLN1602 and DL1606 from Covestro (Leverkusen, Germany); Eternajet® AQ10NJ, 12NJ and 13NJ from UBE (Tokyo, Japan); Superflex® 420, 460, 420NS, 470, and 650 from DKS Co. (Kyoto, Japan); Hydran® WLS-210 and WLS-213 from DIC Co. (Tokyo, Japan).Jettable Adhesive Ink

[0054] In one embodiment, a jettable adhesive ink is an inkjet ink which includes a polymeric resin acting as an adhesive binder and doesn’t contain any colorant, either pigment or dye.

[0055] In one embodiment, a polymeric binder for a jettable adhesive ink is the same as a polymeric binder for a heat-transferable white ink and includes a blend of a polyester polyurethane and a polycarbonate polyurethane. The jettable adhesive ink can be clear, translucent, or slightly white in color. Other components of the ink include aqueous vehicle and additional additives such as water, water-soluble organic solvents, surfactant, pH adjuster, and biocide are in the same scope as described for the heat- transferable white ink and non-white colored ink compositions. Ink properties are set in the same range as well.Blocked Polyisocyanate Crosslinking Agent

[0056] In one embodiment, a heat-transferable white ink and / or a jettable adhesive ink also contains a blocked polyisocyanate crosslinking agent which can chemically react with some or all of the polymer binders, ink solvents, fabric, white and color inks upon heat treatment of the printed article. A blocked polyisocyanate compound is used as a crosslinking agent to enable good adhesion, rub resistance, and wash resistance of the printed article. A useful blocked isocyanate crosslinking agent has at least two important properties: (a) during a heated transfer process, it dissociates / deblocks to generate active polyisocyanate to undergo chemical reactions with active hydrogen containing compounds, including ink’s binder and dispersant polymers with COOH and amines groups, ink solvents and fabrics with hydroxy groups, and any other compounds with active hydrogen capable of reacting with isocyanate, and (b) it is water dispersible or water soluble with hydrophilic segments in the compound so that it can be mixed with other aqueous ink components without phase separation.

[0057] Blocked polyisocyanate crosslinking agents can be obtained by reacting a diisocyanate or polyisocyanate-terminated prepolymer with a ‘blocking agent’ so that isocyanate is deactivated and non-reactive at room temperature. Therefore, ink comprising blocked isocyanate crosslinking agent is stable during storage in liquid form. Only when heated and deblocked, it becomes chemically active and undergoes crosslinking reactions as active isocyanate. There are several blocking agents which are used to produce blocked isocyanates, and these blocking agents determine the deblocking temperature. Specifically, diethyl malonate deblocks at 100-120°C, 3,5- dimethylpyrazole deblocks at 110-120°C, methylethylketoxime deblocks at 120-140°C, and caprolactam deblocks at 160-180°C. The specific deblocking temperature is not particularly limited, but when the temperature is too low, ink may start crosslinking in liquid form which results in short shelf life. When the temperature is too high, ink may not achieve sufficient crosslinking density to achieve desired rub and wash resistance performance. For textile printing, a starting deblocking temperature in the range of from 100 to 150°C is preferred. Aside from the blocking agent employed, there are several key characteristics which define what performance properties a given blocked isocyanate will impart. These characteristics include the type of isocyanate selected (aliphatic or aromatic), the NCO equivalent weight, the %NCO, and the functionality of the isocyanate. Examples of water-based blocked polyisocyanate crosslinker include but are not limited to series Trixene® Aqua Blocked isocyanates Bl 120, BI200, BI201 , BI202, BI220 and BI522 from LANXESS (Cologne, Germany); Imprafix® 2794, 2794 / I, HS-C and TH from Covestro (Leverkusen, Germany); Esajet® 18, and Rolflex® BK9 from Lamberti Group (Gallarate, Italy); and MEIKANATE® DM-6400, TP-10, SU-268A, SU-315V from MEISEI Chemical Works (Kyoto, Japan)

[0058] In one embodiment, a blocked polyisocyanate crosslinking agent is present in an amount of from 0.1 to 5.0 wt% based on the total weight of the ink composition. In one embodiment, a blocked polyisocyanate crosslinking agent is present in an amount of 0.5 wt% or or 0.8 wt% or more based on the total weight of the ink composition.Ink Vehicle

[0059] In one embodiment, a pigmented ink includes an ink vehicle, typically an aqueous ink vehicle. The term “aqueous ink vehicle” refers to an ink vehicle comprisedof water or a mixture of water and one or more organic, water-soluble vehicle components commonly referred to as co-solvents or humectants. Selection of a suitable mixture depends on requirements of the specific application, such as desired surface tension and viscosity, the selected pigment, drying time of the pigmented inkjet ink, and the type of media onto which the ink will be printed.

[0060] Examples of water-soluble organic solvents and humectants include: alcohols, ketones, keto-alcohols, ethers and others, such as thiodiglycol, Sulfolane, 2- pyrrolidone, 1 ,3- dimethyl-2-imidazolidinone and caprolactam; glycols such as ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, trimethylene glycol, butylene glycol and hexylene glycol; addition polymers of oxyethylene or oxypropylene such as polyethylene glycol, polypropylene glycol and the like; triols such as glycerol and 1 ,2,6-hexanetriol; lower alkyl ethers of polyhydric alcohols, such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, diethylene glycol monomethyl, diethylene glycol monoethyl ether; lower dialkyl ethers of polyhydric alcohols, such as diethylene glycol dimethyl or diethyl ether; urea and substituted ureas. The amount of ink vehicle in the ink is typically in the range of from 60 to 95 wt%, and more typically in a range of from 70 to 95 wt%, based on the total weight of the ink.

[0061] The ink vehicle can be made to be rapid drying by including solvents such as glycol ethers and 1 ,2-alkanediols. Glycol ethers include ethylene glycol monobutyl ether, diethylene glycol mono-n-propyl ether, ethylene glycol mono-iso-propyl ether, diethylene glycol mono-iso-propyl ether, ethylene glycol mono-n-butyl ether, ethylene glycol mono-t-butyl ether, diethylene glycol mono-n-butyl ether, triethylene glycol mono- n-butyl ether, diethylene glycol mono-t-butyl ether, 1-methyl-1 -methoxybutanol, propylene glycol mono-t-butyl ether, propylene glycol mono-n-propyl ether, propylene glycol mono-iso-propyl ether, propylene glycol mono-n-butyl ether, dipropylene glycol mono-n-butyl ether, dipropylene glycol mono-n- propyl ether, and dipropylene glycol mono-isopropyl ether. Typical 1 ,2-alkanediols are C4-C6 alkanediols with 1 ,2- hexanediol being most typical. The amount of glycol ether(s) and 1 ,2-alkanediol(s) added is typically in the range of from 1 to 15 wt%, and more typically from 2 to 10 wt%, based on the total weight of the ink.

[0062] Surfactants are commonly added to inks to adjust surface tension and wetting properties. Suitable surfactants include ethoxylated acetylene diols (e.g., the Surfynol® series commercially available from Evonik Industries, Piscataway, NJ), ethoxylated alkyl primary alcohols (e.g., the Neodol® series commercially available from Shell USA, Inc., Houston, TX) and secondary alcohols (e.g., the Tergitol® series commercially available from Dow Chemical Co., Midland, Ml), sulfosuccinates (e.g., the Aerosol® series commercially available from Syensqo, Alpharetta, GA), organosilicones (e.g., the DYNOL™ series commercially available from Evonik) and fluoro surfactants (e.g., the CAPSTONE™ series commercially available from The Chemours Co., Wilmington, DE). Surfactants are typically used in amounts up to about 3 % and more typically in amounts up to 1 % by weight, based on the total weight of the ink.

[0063] Other ingredients, additives, may be formulated into the inkjet ink, to the extent that such other ingredients do not interfere with the stability and jettability of the inkjet ink. This may be readily determined by routine experimentation by one skilled in the art.

[0064] Inclusion of sequestering (or chelating) agents such as ethylenediaminetetraacetic acid, iminodiacetic acid, ethylenediamine-di(o- hydroxyphenylacetic acid), nitrilotriacetic acid, dihydroxyethylglycine, trans-1 ,2- cyclohexanediaminetetraacetic acid, diethylenetriamine-N,N,N',N",N"-pentaacetic acid, and glycoletherdiamine-N,N,N',N'-tetraacetic acid, and salts thereof, may be advantageous, for example, to eliminate deleterious effects of heavy metal impurities.

[0065] Biocides may be used to inhibit growth of microorganisms.Inkjet Ink Sets

[0066] The term “ink set” refers to all the individual inks or other fluids an inkjet printer is equipped to jet. Adhesive inks, heat-transferable white inks and non-white colored inks are considered part of an ink set.

[0067] In one embodiment, the ink set comprises two differently colored inkjet inks, at least one of which is a heat-transferable white ink as described above, and one of which is a jettable adhesive ink as described above.

[0068] In another embodiment, the ink set comprises at least three differently colored inkjet inks, wherein at least one is a cyan inkjet ink, at least one is a magenta inkjet ink, and at least one is a yellow inkjet ink.

[0069] In addition to the colored inkjet inks just mentioned, it is also possible to include a black inkjet ink in the ink set.

[0070] In addition to the Cyan (C), Magenta (M), Yellow (Y), Black (K), White (W) and jettable adhesive inks mentioned above, the ink sets may contain additional differently colored inks, as well as different strength versions of the CMYKW and other inks.

[0071] For example, the ink set of the present invention can comprise full-strength versions of one or more of the inks in the ink set, as well as “light” versions thereof.

[0072] Additional colors for the inkjet ink set include, for example, orange, violet, green, red and / or blue.

[0073] In one embodiment, inkjet ink sets are pigmented inks.

[0074] Jet velocity, separation length of the droplets, drop size and stream stability are greatly affected by the surface tension and the viscosity of the ink. Inkjet inks suitable for use with inkjet printing systems should have a surface tension in a range of from 20 to 70 dyne / cm, or from 25 to 40 dyne / cm at 25°C. Viscosity is in a range of from 1 to 30 cP, or from 2 to 20 cP at 25°C. The ink has physical properties compatible with a wide range of ejecting conditions, i.e. , driving frequency of the pen and the shape and size of the nozzle.

[0075] The inks should have excellent storage stability for long periods. Preferably, inks can sustain elevated temperature in a closed container for extended periods (e.g., 70°C for 7 days) without substantial increase in viscosity or particle size.

[0076] Further, inks should not corrode parts of the inkjet printing device they come in contact with, and should be essentially odorless and non-toxic.

[0077] Inks of the present invention can achieve the beneficial durable properties of washfastness.Recording Medium

[0078] DTF film, or Direct-to-Film film, is a type of transfer film that is used in a DTF printing process. It typically is a clear, transparent PET film that has a special coatingon one side that allows it to bond with DTF ink and to release from the base PET film.In the recording process, an image is first printed onto the film using a DTF printer and DTF ink. The ink is then dried using a heat press or a special drying unit. Once the ink is dried, the film is placed onto the fabric or substrate to be printed, and heat and pressure are applied using a heat press. During the heat transfer process, the ink on the film bonds with the fabric. The DTF film can be peeled away from the fabric once the transfer is complete, leaving behind a full-color image. DTF film is available in a variety of sizes, ranging from small sheets for custom designs to large rolls for mass production. It is compatible with a wide range of fabrics and other substrates. In one embodiment, a DTF film is used to heat-transfer a printed image to a textile fabric.Fabrics include but are not limited to cotton, wool, silk, nylon, polyester and the like, and blends thereof. The finished form of the textile fabric includes, but is not limited to, garments, t-shirts, furnishings such as carpets and upholstery fabrics, and the like.

[0079] Examples of DTF films include, but are not limited to, KODACOLOR® films with various finishes such as Economy Glossy, Premium Matte and Premium Glossy from Kodak (Rochester, NY), Kemafoil KTR® DTF films from Coveme (Bologna, Italy), and DTF films from ECOFREEN® USA (Plano, TX).Image Forming Process

[0080] In one embodiment, a process for digitally printing an image on a DTF substrate and heat-transferring a printed image to a textile fabric. In one embodiment, the process includes the following steps: a) providing the DTF substrate; b) jetting aqueous non-white colored inks on the DTF substrate; c) jetting an aqueous heat-transferable white ink on the aqueous non-white colored inks, wherein the aqueous heat-transferable white ink includes:5-15 wt% titanium dioxide pigment;5 to 25 wt% polyurethane binder, wherein the polyurethane binder is a blend with a ratio in a range of from 0.8:1 to 21 :1 of a polyester polyurethane to a polycarbonate polyurethane;0.1 to 5 wt% blocked isocyanate crosslinker; and0.1-1.5 wt% surfactant;d) heating the DTF substrate to dry the inks; e) laying the DTF substrate on top of the textile fabric with the heat-transferable white ink in contact with the textile fabric; f) pressing the DTF substrate and textile fabric together with heat and pressure; and g) peeling the DTF substrate away with the printed image transferred from the DTF substrate to the textile fabric.

[0081] In one embodiment, the process further includes after peeling in step g): h-1 ) applying additional heat to the textile fabric with the transferred image; h-2) applying additional pressure to the textile fabric with the transferred image; or h-3) applying additional heat and pressure to the textile fabric with the transferred image. In one embodiment, during heat-transfer in step f) a heat-transfer temperature is in a range of from 120 to 180°C and a heat-transfer time is 5 seconds or more.

[0082] In one embodiment, the process further includes after jetting an aqueous heat-transferable white ink and before heating the DTF substrate, jetting an aqueous adhesive ink on the aqueous heat-transferable white ink, wherein the aqueous adhesive ink includes:5 to 25 wt% polyurethane binder, wherein the polyurethane binder is a blend with a ratio in a range of from 0.8:1 to 21 :1 of a polyester polyurethane to a polycarbonate polyurethane;0.1 to 5 wt% blocked isocyanate crosslinker; and0.1-1 .5 wt% surfactant.

[0083] Printing can be accomplished by any DTF (Direct-to-Film) inkjet printer equipped for handling and printing films. Commercial printers include, for example, DTF printers from Cobraflex (Tempe, AZ) and Polytech Inc. (Shenzhen, China).

[0084] A variety of inks and ink sets are available for use with these printers. Commercially available ink sets include, for example, DuPont™ Artistri™ P1600 series inks.

[0085] The amount of ink laid down on the film can vary by printer model, by print mode (resolution) within a given printer and by the percent coverage needed to achievea given color. The combined effect of all these considerations is grams of ink per unit area of film for each color.

[0086] Typically, time interval between step d) and step e) is not defined. It can range from as short as 30 seconds to 12 months or longer depending on process logistics.

[0087] Typically, step g) takes places immediately after step f). It can range from 5 seconds to 5 minutes depending on the types of DTF films. Some films have better peel performances while it is still hot, while some films are easier to peel away after cooling for some time.

[0088] Typically, in step d) the prints are dried with heat, such as disclosed in U.S. Patent Application Publication No. 2003 / 0160851 A1 (the disclosure of which is incorporated by reference herein for all purposes as if fully set forth). Upper temperature is dictated by the blocked isocyanate blocking agent crosslinking temperature. Too high temperature may result in poor adhesion and transfer failure to the fabric due to crosslinking of the images on the film substrate before transferring. Lower temperature is determined by the amount of heat needed to achieve nontackiness of the prints. If the prints are under-dried and tacky, they can stick to the back side of the DTF film when rewinding to a roll after printing and before transferring. Generally, drying temperatures will be at least about 80°C, and preferably not exceeding about 120°C. Time of drying can be about 60 seconds, or about 120 seconds, or about 180 seconds.

[0089] Typically, in step f) the printed DTF film is pressed to the fabric with heat and pressure, such as disclosed in U.S. Patent Application Publication No. 2003 / 0160851 A1 . Maximum temperature and pressing time are dictated by the heat tolerance of the DTF film and fabric. Minimum temperature and pressing time are determined by the amount of heat needed to activate the blocked polyisocyanate crosslinking agent to complete the crosslinking reaction and achieve desired washability. Generally, pressing temperatures will be at least about 130°C, or at least about 150°C, or at least about 160°C. Most of the pressing time in the transfer process generally involves bringing the print up to the desired temperature. Once the print is fully up to temperature, the time under pressure can be brief (seconds).

[0090] The pressures required during the transfer process to achieve improved durability can be very modest. Thus, pressures can be about 3 psig, or at least 5 psig, or at least 8 psig, or at least 10 psig. Pressures of 30 psig and above appears to provide no additional benefit to durability, but such pressures are not excluded.

[0091] Aqueous inkjet ink sets, including jettable adhesive ink, heat-transferable white ink and colored inks, can be used to digitally print images on Direct-to-Film substrates, which can then be heat-transferred onto textile fabrics. In this way, high quality and durable images can be provided on a wide range of textile fabrics without exposure to thermoplastic polyurethane powders, thus avoiding the health and safety concerns of working with these powders.

[0092] The invention is further illustrated by, but not limited to, the following examples, in which parts and percentages are by weight unless otherwise noted.EXAMPLESTest MethodsMechanical Properties

[0093] Elongation at break and tensile strength of polyurethane resin by itself or blends of two polyurethane resins were obtained under the conditions described below. About 25 g of resin or resin blend was applied onto a Teflon® sheet lined petri dish and dried for 3 days at room temperature, and then dried for a further 24 hours at 60°C under vacuum and additional 2 hours at 85°C under vacuum. This process resulted in fully dried resin films of about 500 pm thickness. Films were then cut into rectangular pieces 6.45 mm in width and 80 mm in length. Using a tensile tester (Instron® model #5943, Norwood, MA) at a measurement temperature of 25°C and pulling rate of 200 mm / min, resin films were pulled until fracture. Elongation at break and maximum tensile strength were recorded.Ink Binders, Crosslinking Agents and Surfactant

[0094] Takelac™ W6110 polycarbonate polyurethane resin (Tg= -20°C) from Mitsui Chemicals (Tokyo, Japan).

[0095] Impranil® DL1618 polyester polyurethane resin (Tg= -4°C) from Covestro (Leverkusen, Germany).

[0096] Esajet 4518 polyester polyurethane resin (Tg= -37°C) from Lamberti Group (Gallarate, Italy).

[0097] Imprafix® 2794 and 2794 / I blocked polyisocyanate crosslinking agents from Covestro (Leverkusen, Germany).

[0098] BYK-348 polyether silicone surfactant from BYK-Chemie GmbH (Wesel,Germany).Preparation of Jettable Adhesive Ink

[0099] Jettable adhesive inks shown in Table 1 were prepared using standard procedures in the inkjet art. Ingredient amounts are in weight percent of the final ink. Polymer binders and Imprafix® blocked isocyanate crosslinking agent are on a dried weight basis. As an example of adhesive ink preparation, the ink vehicle was prepared and added with stirring to the aqueous polymer binder and Imprafix® blocked isocyanate crosslinking agent and stirred until the ink was well mixed.Table 1Heat-Transferable White Inks

[0100] Heat-transferable white inks were made according to standard procedures in the inkjet art. Ingredient amounts are in weight percent of the final ink. Polymer binders are on dried weight basis. White TiO2 dispersion is on a TiO2 weight basis. TiO2 pigment dispersion, as described in U.S. Patent Application Publication No.2007 / 0060670 A1 , was employed. As an example of heat-transferable white ink preparation, the ink vehicle was prepared and added with stirring to the aqueous ink binder. After stirring until a homogeneous mixture was obtained, the solution wasadded to the pigment dispersion and mixed until homogeneous again. Heat- transferable white ink formula, with and without blocked isocyanate crosslinking agent with the same combinations of solvents and surfactants were prepared. Final inks employing various comparative and inventive Plls were made from these ink formulas. The compositions of the heat-transferable white inks are summarized in Table 2 and some mechanical properties of the binders used in the white inks, but without the white pigment, are shown in Table 3. Comparative White Ink-1 and Comparative White Ink-2 contain the polyurethane binder blend with a ratio of polyester polyurethane to polycarbonate polyurethane outside of the desired range. Comparative White Ink-3 and Comparative White Ink-4 contain an unblended polyurethane binder and do not have the crosslinking agent.

[0101] As polycarbonate polyurethane (Takelac™ W6110) weight increases, the film’s tensile strength increases with a reduction of elongation-at-break, indicating a stronger film with less flexibility. Although not bound by theory, it is believed stronger film improves rub and washfastness but less flexibility negatively impacts adhesion to the fabric during the transfer process. Balanced mechanical properties will result in optimal performances of the printed fabric article.Table 2Table 3Non-White Colored Inks

[0102] A cyan ink was prepared according to procedure disclosed in U.S. Patent Application Publication No. 2017 / 0355866 A1 , the disclosure of which is incorporated by reference herewith for all purposes as if fully set forth.

[0103] A yellow ink was prepared in a similar fashion as the cyan ink, replacing the cyan pigment with yellow pigment PY155.

[0104] A magenta ink was prepared in a similar fashion as the cyan ink, replacing the cyan pigment with magenta pigment PR122.

[0105] A black ink was prepared in a similar fashion as the cyan ink, replacing the cyan pigment with carbon black pigment.Printing and Heat-Transfer

[0106] Using a DTF printer (Polytech DTF 602 printer, Shenzhen, China), Cyan, Magenta, Yellow and Black inks were first printed at 100% ink coverage on a DTF film (Cobraflex, Tempe, AZ), followed by heat-transferable white ink at 100% ink coverage on top of the non-white colored ink layer. There was no drying between the different ink layers and the jetting time interval was generally less than 1 minute between different colors and heat-transferable white inks. Inks on the DTF film was subsequently dried by moving the printed film through a curing oven (DragonAir™ Fire 3611 , Brown Manufacturing Group, Inc., Wyoming, Ml) on a conveyor belt for 3 minutes at 125°C. The dried printed DTF film was then laid on top of a black cotton T-shirt supplied by Cotton Heritage with the heat-transferable white ink layer in contact with the T-shirt.The DTF film and T-shirt were then pressed together with a DTF heat press (Cobraflex) at 165°C for various set times with air pressure set at 85 psi. The set times ranged from 20 to 120 seconds. Longer press time leads to better adhesion and washfastness. Shorter time is more desirable for productivity and less risk to damaging the fabric,particularly for polyester fabrics. Films were then peeled away with the white and color ink images transferred to the T-shirt. Time intervals between taking the laminate off the heat press and peeling the films off varied from about 30 seconds to 5 minutes depending on the types of DTF films. To measure washfastness of the transferred image, the T-shirt was subject to two cycles of laundering. Image quality was examined and given a rating from 1 to 5, with 5 as the best. If image quality was intact and no ink peeled from the fabric, the washfastness rating was 5. If no ink peeled from the fabric but image appeared wrinkled from partial delamination, the washfastness rating was 4. If 5 to 10% of the image was peeled from the fabric and pin holes were observed, the washfastness rating was 3. If about 50% of the image was peeled from the fabric, the washfastness rating was 2. If more than 50% of the image was washed off from the fabric, the washfastness rating was 1 .

[0107] Results in Table 4 below show that heat-transferable white inks containing a polyurethane binder blend had much improved washfastness over conventional white inks. Although the Comparative White Ink-3 also had good washfastness, the color of the ink was poor.Table 4

[0108] Using the same printing and heat transfer described above, but jetting an aqueous adhesive ink on the aqueous heat-transferable white ink before transfer of the image to the textile fabric results in improved adhesion of the heat-transferable white ink to the textile fabric. In addition, the inks with blended polyurethane binder (White Ink-3 and White Ink-4) have improved adhesion over an ink with unblended binder (Comparative White Ink-4). These results are summarized in Table 5.Table 5

Claims

CLAIMSWhat is claimed is:1 . An aqueous heat-transferable inkjet ink set comprising: a heat-transferable white ink comprising:5-15 wt% titanium dioxide pigment;5 to 25 wt% polyurethane binder, wherein the polyurethane binder is a blend with a ratio in a range of from 0.8:1 to 21 :1 of a polyester polyurethane to a polycarbonate polyurethane;0.1 to 5 wt% blocked isocyanate crosslinker; and0.1 -1.5 wt% surfactant; and non-white colored inks, wherein the aqueous heat-transferable ink set is adherable to a textile surface by heat-transfer.

2. The aqueous heat-transferable inkjet ink set of claim 1 , further comprising a jettable adhesive ink, wherein the jettable adhesive ink comprises:5 to 25 wt% polyurethane binder, wherein the polyurethane binder is a blend with a ratio in a range of from 0.8:1 to 21 :1 of a polyester polyurethane to a polycarbonate polyurethane;0.1 to 5 wt% blocked isocyanate crosslinker; and0.1-1.5 wt% surfactant.

3. The aqueous heat-transferable inkjet ink set of claim 2, wherein the polyurethane binder of the heat-transferable white ink and the polyurethane binder of the jettable adhesive ink are the same.

4. The aqueous heat-transferable inkjet ink set of claim 2, wherein the blocked isocyanate crosslinker of the heat-transferable white ink and the blocked isocyanate crosslinker of the jettable adhesive ink are the same.

5. The aqueous heat-transferable inkjet ink set of claim 2, wherein the surfactant of the heat-transferable white ink and the surfactant of the jettable adhesive ink are the same.

6. The aqueous heat-transferable inkjet ink set of claim 1 , wherein the polyurethane binder has a Tgof 10°C or lower.

7. The aqueous heat-transferable inkjet ink set of claim 1 , wherein colorants for the non-white colored inks comprise non-white pigments.

8. The aqueous heat-transferable inkjet ink set of claim 7, wherein the colorants for the non-white colored inks further comprise dispersants.

9. A process for digitally printing an image on a Direct-to-Film (DTF) substrate and heat-transferring a printed image to a textile fabric comprising: a) providing the DTF substrate; b) jetting aqueous non-white colored inks on the DTF substrate; c) jetting an aqueous heat-transferable white ink on the aqueous non-white colored inks, wherein the aqueous heat-transferable white ink comprises:5-15 wt% titanium dioxide pigment;5 to 25 wt% polyurethane binder, wherein the polyurethane binder is a blend with a ratio in a range of from 0.8:1 to 21 :1 of a polyester polyurethane to a polycarbonate polyurethane;0.1 to 5 wt% blocked isocyanate crosslinker; and0.1-1.5 wt% surfactant; d) heating the DTF substrate to dry the inks; e) laying the DTF substrate on top of the textile fabric with the aqueous heat- transferable white ink in contact with the textile fabric; f) pressing the DTF substrate and textile fabric together with heat and pressure; and g) peeling the DTF substrate away with the printed image transferred from the DTF substrate to the textile fabric.

10. The process of claim 9, further comprising after peeling in step g): h-1 ) applying additional heat to the textile fabric with the transferred image; h-2) applying additional pressure to the textile fabric with the transferred image; or h-3) applying additional heat and pressure to the textile fabric with the transferred image.11 . The process of claim 9, wherein in step f) a heat-transfer temperature is in a range of from 120 to 180°C and a heat-transfer time is 5 seconds or more.

12. The process of claim 9, further comprising after jetting an aqueous heat- transferable white ink and before heating the DTF substrate, jetting an aqueousadhesive ink on the aqueous heat-transferable white ink, wherein the aqueous adhesive ink comprises:5 to 25 wt% polyurethane binder, wherein the polyurethane binder is a blend with a ratio in a range of from 0.8:1 to 21 :1 of a polyester polyurethane to a polycarbonate polyurethane;0.1 to 5 wt% blocked isocyanate crosslinker; and0.1-1.5 wt% surfactant.

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